'Pretty Little Liars' Star Keegan Allen on What to Expect in Tonight's Finale

— -- "Pretty Little Liars" star Keegan Allen says fans will be satisfied with tonight's season finale.

"Expect a lot of twists and turns and something that will propel the show forward," Allen, who plays police officer Toby Cavanaugh, told ABC News. "I have a feeling that a lot of the viewership will be satisfied tonight because it seemingly opens a final big can of worms that we will explore in season 7."

One of the biggest reveals in the finale that fans are looking forward to is the twin theory that both the show and its executive producer Marlene King have teased throughout the series.

"There's a twin theory -- I can promise you -- once Charlotte was revealed as 'A' there was a lot of speculation on twin theory, and tonight it's kind of explored," Allen, 26, said. "And the audience will be excited for sure about what happens."

Allen's character Toby, and Spencer Hastings, known together as "Spoby," will also finally reunite in tonight's episode. Toby and Spencer, the latter played by Troian Bellasario, spent much of the season apart because of their breakup before the show's five year time jump. Their breakup was explained in a flashback that showed the couple had a pregnancy scare while Spencer was at Georgetown.

"It was a really painful scene to shoot. It was very intense," Allen said. "This was something that went right out there and shed some light on real subjects that people deal with. Hats off to Freeform for doing that."

Allen said fans of Ezra and Aria, Emily and Alison, and Hanna and Caleb should also be excited about the finale.

"There's a lot of relationships going on with the show and the structure with the show, and it will be interesting for the fans to see where these characters have grown with and without each other," said Allen.

Allen will be live-tweeting during the show tonight and says he's grateful for the fans' support.

"It's quite a testament to the show that we're in the end of our sixth season, and fans, the audience and the cast and crew are at a point where it's still insane," said Allen.

"There's so many twists and turns that's still happening and we're in the end of our 6th season, and tonight is no different from any amazing season finale we've had in the show."

"Pretty Little Liars" airs tonight at 8 p.m. ET on Freeform, the new name for ABC Family.

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